Plasma bubbles: a route to sustainable chemistry

Atmospheric plasma discharges are finding increased applications in addressing environmental challenges including water purification, chemical synthesis and biotechnology. An effective means of interfacing the reactivity of plasma gas discharges with liquids is needed to enhance liquid phase chemical reactions. Plasma discharges in bubbles has been considered as an innovative solution for achieving this goal potentially offering electrically driven, sustainable chemistry with low energy consumption and the unique benefit of maintaining a large volume discharge under the liquid surface. Here we provide a concise review on the state-of-art for research on plasma-bubble interactions and a perspective for future research.

Picosecond high-current discharge pumping of gaseous media emitting VUV-UV

The possibility of creating small picosecond lasers in the VUV-UV spectral range by pumping by a high-current volume discharge of gaseous media (Xe and N2) at a pressure of 1-3 atm is investigated. Generation of picosecond (200 ps) powerful (1.2 MW) pulses at a wavelength of 337 nm at an N2 pressure of 1–3 atm has been achieved. Based on studies of high-current volume picosecond discharges in xenon, using VUV-UV spectroscopy, the presence of short-lived absorption of VUV radiation by discharge plasma was observed. A mechanism for the suppression of the formation of Xe 2 * dimers due to thermal effects at the stage of recombination of electrons with Xe+ ions at a plasma temperature of 105 K with a pulsed pump of 200 ps duration was suggested.

Formation mechanism of clogging of dredge slurry under vacuum preloading by using digital image technology

Vacuum preloading combined with prefabricated vertical drains (PVDs) system has been widely used to improve the soft clay with high water content. Clogging is usually formed around the PVDs during the vacuum preloading, impeding the propagation of the vacuum pressure and slowing down the consolidation process. In order to understand the forming mechanism of the clogging, particle image velocimetry (PIV) technique and particle tracking velocimetry (PTV) technique were adopted in the model test of vacuum preloading test. Through this study, three stages can be identified from the results of water volume discharge rate and maximum displacements versus time. In the first stage, the soil around the PVD is horizontal consolidated, which leads to the rapid formation of clogging. In the second stage, the formation of clogging slows down due to the loss of vacuum pressure, which further reduces the drainage. In the third stage, the clogging tends to be stable, and the drainage consolidation rate is significantly reduced. PTV results show that there is difference in the displacement of large and small particles during improvement. Two methods were proposed to estimate the thickness of clogging zone, reflecting a growing layer of clogging zone compressed around the PVD. This study provides new insights to investigate the formation mechanism of clogging during vacuum preloading test.

The dynamics of the formation of initial stages of a transverse nanosecond discharge with an extended slot cathode in argon

The dynamics of the main characteristics of a limited nanosecond discharge in an extended slot cathode in argon at the values of the applied voltage to the electrodes close to the values of the voltages of the formation of a volume discharge are studied by numerical simulation. It is shown that this type of discharge can be used to create an extended dense plasma column with a high density of charged and excited particles. The analysis of the spatiotemporal dynamics of development of the electron density and the electron energy distribution function was carried out. It is shown that the high-energy electrons are formed at the front of the ionization wave due to the hollow-cathode effect.

Mechanistic Model for the Design and Operation of an Intermittent Gas Lift System for Liquid Loaded Horizontal Gas Wells

Removing stagnant liquid in a loaded horizontal gas well remains an unsolved challenge. Current practices for horizontal well deliquification are limited in terms of reliability and continuity, resulting on increased OPEX and CAPEX, behind down time and additional equipment installation. Experimental evaluation of a proposed artificial lift method for horizontal well deliquification, showed average removal efficiencies of 75% of the stagnant liquid volume. The experimental facility consisted of an experimental flow loop, that replicates conditions of liquid-loaded horizontal wells, with a horizontal section of 40 feet and a vertical section of 40 feet. The method is based on the chamber lift principles, using intermittent injection of gas at high pressure and low volumetric flow rates to the horizontal section of the well. Removal efficiency increased by 12% by using saccharidic additives and sodium chloride, to increase the surface tension between the injected gas (compressed air) and the liquid (water). This work presents a mechanistic model of the proposed artificial lift method, based on the momentum balance of the gas and the liquid slug flowing along the horizontal and vertical sections of the system, including numerical regressions for the prediction of the surface tension and viscosity of the liquid mixture as a function of temperature and the concentration of the tested additives. The model is used to determine the required available injection pressure at surface, and the location of the valve mandrel, as same as to estimate the removed liquid volume, discharge volumetric rate, and discharge pressure of the liquid slug at the surface facilities. The model is validated against experimental data obtained from the experimental flow loop.

Combined conchal cartilage islet-periosteum and posterior based pedicled flap obliteration: a comparison with unobliterated mastoid cavities

<p><strong>Background:</strong> Aim of the study was to compare the outcomes of a new technique of mastoid cavity obliteration with open mastoid cavity.</p><p><strong>Methods:</strong> 90 patients diagnosed with chronic otitis media (active squamosal variety) and planned to undergo surgery between 2016-2018 were randomly assigned into two groups of 45 patients. One group underwent canal wall down matoidectomy followed by cavity obliteration with posteriorly based vascularised flap with mastoid cortex periosteum plus conchal cartilage composite graft and the other underwent the same surgery but without any obliteration. The two groups were compared in terms of cavity volume, discharge, epithelisation, wax formation, subjective sensation of vertigo and post-operative air-bone gap at 1 year.</p><p><strong>Results:</strong> Cavity obliteration in post-canal wall down setting significantly reduced the post-operative cavity volume and need for cavity debridement with better epithelisation, less incidence of discharge, vertigo on caloric stimulation when compared to open cavity. The post-operative air-bone gap in obliterated cavities was better but not statistically significant.</p><p><strong>Conclusion: </strong>Cavity obliteration has definite advantages over open cavity in terms of healing but no significant differences in long-term audiological outcomes.</p>

Numeric Study on the Influence of Sluice-Gate Operation on Salinity, Nutrients and Organisms in the Jiaojiang River Estuary, China

The estuary—located in the joint zone between river and ocean—has created unique ecosystems and rich biodiversity due to its complex habitat conditions. As the critical period for the growth and reproduction of estuarine organisms, the flood season is also crucial for estuary sluice to play a role in flood control and drainage. This study aims at proposing an ecological scheduling scheme that comprehensively considers the adverse factors brought by draining of the estuarine sluice to maintain different ecological functions of the Jiaojiang River estuary. A two-dimensional mathematical model in MIKE 21 was used to ascertain the change of salinity and nutrients in the study area, and results were analyzed to understand the impact of draining on estuarine organisms. Based on an analysis of the change and redistribution of salinity and nutrients, the sea area could be divided into three parts during the operation of the estuarine sluice: nearshore area with low-salt and high eutrophication, medium mixed salinity under nitrogen limitation area and high-salt under phosphorus limitation area. The aquaculture area was alternately situated in the mesohaline (>5.0‰–18.0‰) and polyhaline (>18.0‰) zones. The after-effects of salinity change—including the lowest value and the sharp change of salinity, especially the sharp change of salinity (11.8‰–12‰) caused by large-volume discharge—would affect the growth of organisms to a certain extent, but would not be lethal. Moreover, a high-incidence red tide area was determined to be formed within 8–14 km away from the estuarine sluice after the sluice opening, and the area of this zone was firmly related to the opening schemes. The study suggested that the proposed sluice should choose the mode of draining frequent with the small flow at neap tide in order to reduce the stress of sluice construction and operation on mariculture organisms and phytoplankton in Jiaojiang River estuary on the strength of the ecological restoration measures for estuary and riparian zones.